Eric,
Welcome to the forum and if you’ve been seeking around recently, you may have found a thread about what to do after the ACPP. The MOST COMMON way and “traditional way” (today) is instructing, but what raises my eyebrow is why are you only looking at ATP for instructing? A few reasons ATP would not select you as a candidate to go through INDOC is if you were in bad standing, multiple failed checkrides, poor performance background. However, MANY flight schools are looking for instructors, just without the perks of ATP.
There are other routes that you can do to build time such as aerial photography, firefighting, banner towing, etc. CFI is the most common; however, there are obviously other avenues, but this is a short list found under 14 CFR 119.1(e) :
As per finding employment, Google, Facebook, and Climbto350 are just a few ways of coming in contact with recruiters. I would also mentioned networking at your local FBO and making friends, acquiring business cards are also a few ways to meet employers.
Brady